Antistatic composition and fiber made therefrom

ABSTRACT

1. AN ANTISTATIC COMPOSITION OF MATTER COMPRISING A HIGH MOLECULAR WEIGHT FIBER-FORMING POLYCARBONAMIDE WHEREIN THE RECURRING CARBONAMIDE LINKAGES ARE AN INTEGRAL PART OF THE POLYMER CHAIN, SAID POLYCARBONAMIDE BEING EITHER A COPOLYMER OF AT LEAST TWO DIFFERENT POLYCARBONAMIDE-FORMING SUBSTANCES OR A MELT BLEND OF AT LEAST TWO DIFFERENT POLYCARBONAMIDE POLYMERS, SAID POLYCARBONAMIDE BEING COMPOSED OF ABOUT 6-24 WEIGHT PERCENT AROMATIC NUCLEI AND A HIGH MOLECULAR WEIGHT POLY(ALKYLENE ETHER) AS A DISTINCT PHASE IN THE FORM OF SMAALL ELONGGATED PARRTICLES FROM 1 TO 15 PERCENT BASED ON THE WEIGHT OF THE COMPOSITION FORMED BY THE ESTER INTERCHANGE REACTION OF   R-OOC-Y-COO-R   WHEREIN R IS AN ALKYL RADICAL OF 1 TO 4 CARBON ATOMS AND Y IS A DIVALENT ORGANIC RADICAL SELECTED FROM THE GROUP CONSISTING OF   -(PHENYLENE)-, -(NAPHTHALYENE)-   AND A LINEAR OR BRANCHED ALKYLENE RADICAL OF 1 TO 20 CARBON ATOMS; AND   (HO-(A-O)N-R&#39;&#39;(-R&#34;)(-X))2-N-R&#39;&#39;-(O-A)N-OH   WHEREIN R&#39;&#39; IS A LINEAR OR BRANCHED C2-C4 ALKYLENE RADICAL, R&#34; IS A C12-C24 ALKYL RADICAL, A IS A LINEAR OR BRANCHED C2-C4 ALKYLENE RADICAL, THE SUM OF THE N&#39;&#39;S IS ABOUT 25 TO 7575, X IS HYDROGEN OR AN ALKYL RADICAL OF 1 TO 4 CARBON ATOMS; AND THE MOL RATIO OF (A) TO (B) IS FROM ABOUT 1:9 TO ABOUT 1:1.

United States Patent US. Cl. 260-857 PG 7 Claims ABSTRACT OF THEDISCLOSURE An antistatic composition is provided suitable for beingshaped by melt spinning into resilient fibers. Such fibers can be usedto make an antistatic carpet structure having a maximum body voltage fora human Walking thereon and wearing leather shoes of less than 3,000volts at 20% relative humidity and 72 F. The antistatic composition iscomposed of a high molecular weight fiberforming polycarbonamidecomposed of about 6-24 weight percent aromatic nuclei and a highmolecular weight non-fiber-forming poly(alkylene ether) compound. Thepolycarbonamide is either a copolymer of at least two differentpolycarbonamide-forming substances or a melt blend of at least twodifierent polycarbonamide polymers. The polyether is present in amountof about 115 percent based on the weight of the composition and isdispersed in the composition as a distinct phase in the form of smallelongated particles. At least 50% of the molecular weight of thepoly(alkylene ether) compound is composed of repeating alkylene oxideunits.

BACKGROUND OF THE INVENTION It is well known that static electricity isgenerated and transferred as one walks on conventional carpet structuresmade from either synthetic fibrous material or natural fibrous material.The more severe problems occur when the carpet pile is made of asynthetic polymer, such as nylon which is a fiber-formingpolycarbonamide wherein the recurring carbonamide linkages are anintegral part of the polymer chain. As one walks on a carpet structure,electron transfer occurs. When a person walking across such a surfacelater becomes grounded, a discharge of electrons occurs through thatpart of the individuals body which by chance comes in contact with theground. The discharge may occur by touching a door knob, metal bookcaseor the like. When the voltage build-up exceeds, 3,000 volts, theelectric shock can cause personal discomfort.

The tendency for static electricity to build-up on a carpet greatlyincreases as the relatively humidity of the ambient air decreases. Manyapproaches have been taken to reduce the static problems of carpets madeof synthetic filaments or fibers. None of these have provided anentirely suitable carpet structure which is lastingly essentially staticfree at 20% or less relative humidity. Substances have been placed onthe surface of the fiber, but the elfectiveness of such treatment isonly temporary. Many different antistatic additives have beenincorporated in carpet yarn with varying degrees of success.Unfortunately, when the carpet is constructed of such yarn, voltagesabove 3,000 volts at 20% relative humidity will occur on a personwalking thereover, unless an undesirable amount of antistatic additiveis placed in the polymer. As one adds more and more antistatic additive,the voltage build-up is accordingly reduced. But, as more and moreantistatic additive is used, the spinnability of the polymer issignificantly reduced; and the fibers made therefrom become easilymatted down because the resistance to crushing of the pile is very muchlowered. It has been suggested to randomly intermingle metal fibersamong the synthetic fibers. This approach gives rise to considerableadded cost and product non-uniformities. It has been taught in the artto incorporate electrically conductive carbon black in latex applied tothe underside of the carpet backing with the pile of the carpetcontaining or not containing an antistatic additive. Using conductivecarbon black in the latex alone without modifying the pile fibers helpsbut does not reduce the electric build-up to below the 3,000 volt levelreferred to above; On the other hand, using conductive carbon black inthe latex and a pile made of synthetic polymer fibers having knownantistatic additives incorporated therein is not only expensive but whensuificient amount of the additive is used the fibers lose theirresiliency.

In accordance with the present invention, a polymeradditive combinationis provided so that the composition thereof is not only lastinglyantistatic but fibers made therefrom are at least as resilient as nylonfibers to which no antistatic additive has been incorporated.

SUMMARY OF THE INVENTION The antistatic composition of the presentinvention can be shaped into films and filaments. Such filaments arecharacterized by having resistance to matting and can be used as thepile material in a conventional carpet structure that provides a maximumbody voltage build-up for a human walking thereover of at most 3,000volts even at relative humidities as low as 20% at 72 F. The com--position is composed of a high molecular weight fiberformingpolycarbonamide and a high molecular weight non-fiber-formingpoly(alkylene ether) compound. The molecular weight can range from 600to 30,000 and higher. The polycarbonamide is composed of about 6-24-weight percent aromatic radicals. The polycarbonamide is a copolymer ofat least two different polycarbonamideforming substances or a melt blendof at least two different polycarbonamide polymers. The polyether ispresent in amount of l-l5 percent based on the weight of the compositionand is dispersed in the composition as a distinct phase in the form ofsmall elongated particles.

DETAILED DESCRIPTION OF THE INVENTION The composition of the presentinvention is basically a specific class of polycarbonamides renderedantistatic by having incorporated therein poly(al'kylene ether)compounds. It is important to the attaining of the unexpected low levelsof static build-up and the high resistance to matting in fiber form thatthe polycarbonamide is fiberforrning and is either a copolymer of atleast two different polycarbonamide-forming substances or a melt blendof at least two ditferent polycarbonamides. As indicated above,polycarbonamides may generically be called nylons and have recurringcarbonamide linkages as an integral part of the polymer chain. It isalso important that 6-24 weight percent of the polycarbonamide becomposed of aromatic nuclei. The presence of the aromatic radicalssurprisingly contributes to the improved electrical properties as Wellas' to the resistance to matting of filaments made therefrom.

The aromatic moieties of the polycarbonamides may be a single ring, afused ring or a multi-nuclear aromatic ring system which can be eitherhomocyclic or heterocyclic. Preferably, it is homocyclic and morepreferably it is carbocyclic. Representative of the divalent aromaticradicals constituting a substantial part of polycarbonamide are thefollowing:

C-- NE NH- ---O NH- etc. Preferably the functional aromatic radical isThe polycarbonamide can be a random copolyamide formed from at least twodifferent polycarbonamideforming substances. Among these substances thatare preferred are:

Also included are random copolymers of p-aminobenzoic acid andhexamethylene adipamide. Instead of hexamethylene diamine one may use inwhole or in part pphenylene diamine.

The polycarbonamides can be a melt blend or dispersion of two or morefiber-forming polymers. Among the blends that are preferred are:

(a) polyhexamethylene adipamide and polyhexamethylene terephthalamide;

(-b) polyhexamethylene adipamide and polyhexamethylene isophthalamide;

(c) polycaproamide and polyhexamethylene terephthalamide;

(d) polycaproamide and polyhexamethylene isophthalamide;

(e) polyhexamethylene adipamide, polyhexamethylene terephthalamide, andpolyhexamethylene isophthalamide;

(f) polycaproamide, polyhexamethylene terephthalamide, andpolyhexamethylene isophthalamide; and (g) polyhexamethylene adipamide,caproamide, and polyhexamethylene terephthalamide.

Dispersed as a separate and distinct phase in the polycarbonamide is ahigh molecular weight non-fiber-forming poly(alkylene ether) compound.The compound in the polycarbonamide matrix takes the form of elongatedparticles of 0.05 to 1.5 microns in diameter and at least 15 micronslong. The poly(alkylene ether) may be added prior to, during or afterthe polycondensing of the polycarbonamide-forming substances. In orderto obtain the high antistatic performance, the p0ly(alkylene ether)compound should be made up of at least 50% by weight of repeatingalkylene oxide units. The alkylene oxide units may be ethylene oxide,propylene oxide, butylene oxide, etc.

The most preferred poly(alkylene ether) additive is formed by the esterinterchange reaction of where R is an alkyl radical of 1 to 4 carbonatoms and Y is a divalent organic radical selected from the group of anda linear or branched alkylene radical of 1 to 20 carbon atoms; and

wherein R is a linear or branched C -C alkylene radical, R" is a C -Calkyl radical, A is a linear or branched C -C alkylene radical, the sumof ns is about 25 to 75, X is hydrogen or an alkyl radical of l to 4carbon atoms; and the mol ratio of (a) to (-b) is from 1:9 to about 1:1.

The static measurement tests used in the following examples wereconducted as follows. The testing was done in a controlled humidity room(20 RH.) maintained at 72i2 F. A 3 ft. x 12 ft. carpet was placed on aconventional waffie rubber carpet pad which lay on the concrete floor ofthe testing room. The human subject, wearing shoes with leather solesand heels, walked on the carpet sample. The subject carried a 1000:1 kv.voltage divider probe. From the probe a lead run to the input of aKeithley 610 C electrometer. The output of the electrometer was then fedto a strip chart recorder. As the subject walked, the voltage increasedto a steady-state maximum voltage after 20 to 30 steps. The data givenbelow are the average body build-up measurements on two subjects.

EXAMPLE I A random copolymer of hexamethylene adipamide andhexamethylene terephthalamide was prepared in an autoclave. Thecopolymer contained 20 weight percent hexamethylene terephthalamideunits and had a relative viscosity of 32 when measured in formic acid at25 C. The polymer was cut into flake suitable for feeding a conventionalscrew melter-extruder.

A poly(alkylene ether) wax (molecular weight-6250) compound was formedby the ester interchange reaction and wherein R is a C -C saturatedaliphatic radical, n is an integer, the sum of the ns being about 50,the mol ratio of (a) to (b) being 1:1.

The flake of the random copolymer was introduced into a melt screwextruder device. Both the rate of introduction of flake and thepoly(alkylene ether) compound and extrusion of the molten polymer weremaintained at 355 pounds per hour. The flake was fed to the inlet end ofthe screw extruder and heated to 285 C. to melt the same. Thepoly(alkylene ether) compound was metered into the molten polymer nearthe exit end of the screw extruder in an amount to provide in thepolymer 7.2% by weight of the poly(alkylene ether) compound. Thecompound became dispersed as a separate phase in the polymer. Theresulting molten composition was forced through trifurcated holes in aspinnerette of a conventional spinning machine to form a threadlinecomposed of 136 filaments having an ultimate drawn total denier of 2460.A small amount of lubricant was applied to the surface of the filaments.The undrawn filaments of trilobal cross section were collected onbobbins. The bobbins were stocked on a multiple position gear-texturingmachine as shown in US. Pat. 3,456,610. The yarn was draw-textured onthis machine and collected. The yarn was then tufted into a non-wovenpolypropylene carpet backing to form a pile fabric. The backing had areinforcing scrim. The pile was level loop of A in. pile height andweighed 22 ounces per square yard. An aqueous dispersion of conventionallatex was applied to the backing which was thereafter dried.

The carpet was tested for static build-up on a human subject inaccordance with the procedure given above. The voltage build-up was only2,600 volts. The carpet had an excellent appearance and had noticeableresistance to matting.

EXAMPLE II In comparison, a homopolymer of hexamethylene adipamide wasprepared and spun into similar filaments. The filaments weredraw-textured and tufted into carpet of the same structure as Example I.It was found that under similar test conditions the voltage build-up onthe carpet was 15,000 volts.

EXAMPLE III In this example a random copolymer of hexamethyleneadipamide and hexamethylene terephthalamide was prepared as in Example Ibut the content of the latter substance was increased to 28 weightpercent. The same poly- (alkylene ether) wax in the same amount as inExample I was incorporated into the copolymer prior to being spun intofilaments. The filaments were draw-textured and tufted into a carpet asin Example I. It was found under similar test conditions that thevoltage build-up on the carpet was 1,960 volts.

EXAMPLE IV In this example the random copolymer was 80% hexamethyleneadipamide and hexamethylene terephthalamide. The same poly(alkyleneether) wax was added to the copolymer as in Example I. However, in thiscase the amount of wax was reduced to 5.5 weight percent. Filaments werespun therefrom, draw-textured and tufted into a carpet as in Example I.It was found that under similar test conditions the voltage build-up onthe carpet was 2,900 volts.

EXAMPLE V In this example the random copolymer was 80% hexamethyleneadipamide and 20% hexamethylene terephthalamide. The same poly(alkyleneether) wax was added to the copolymer as in Example I. The amount of waxwas 7.2% by weight. However, 75 p.p.m. copper in compound form was addedto the polymer. Filaments were spun therefrom, draw-textured and tuftedinto carpet as in Example I. It was found that under similar testconditions the voltage build-up on the carpet was 2,300 volts.

What is claimed is:

1. An antistatic composition of matter comprising a high molecularweight fiber-forming polycarbonamide wherein the recurring carbonamidelinkages are an integral part of the polymer chain, said polycarbonamidebeing either a copolymer of at least two differentpolycarbonamide-forming substances or a melt blend of at least twodifferent polycarbonamide polymers, said polycarbonamide being composedof about 6-24 weight percent aromatic nuclei and a high molecular weightpoly(alkylene ether) as a distinct phase in the form of small elongatedparticles from 1 to 15 percent based on the weight of the compositionformed by the ester interchange reaction of (a) ROCYCOR wherein R is analkyl radical of 1 to 4 carbon atoms and Y is a divalent organic radicalselected from the group consisting of and a linear or branched alkyleneradical of 1 to 20 carbon atoms; and

' to about 1:1.

2. The composition of claim 1 wherein the aromatic nuclei is 3. Thecomposition of claim 1 wherein the polycarbonamide is a randomcopolyamide formed from the polycarbonamide-forming substances selectedfrom the group consisting of (a) hexamethylene adipamide andhexamethylene terephthalamide;

(b) hexamethylene adipamide and hexamethylene isophthalamide;

(c) caproamide and hexamethylene terephthalamide;

(d) caproamide and hexamethylene isophthalamide;

(e) hexamethylene adipamide, hexamethylene terephthalamide andhexamethylene isophthalamide;

(f) caproamide, hexamethylene terephthalamide and hexamethyleneisophthalamide; and

(g) hexamethylene terephthalamide, caproamide and hexamethyleneterephthalamide.

4. The composition of claim 1 wherein the polycarbonamide is a meltblend of polymers selected from the group consisting of (a)polyhexamethylene adipamide and polyhexamethylene terephthalamide;

(b) polyhexamethylene adipamide and polyhexamethylene isophthalamide;

7 '(c) polycap'r'oamide and polyhexamethylene terephthal'amide;

' (d) polycaproamide and polyhexamethylene isophthalamide;' (e)polyhexamethylene adipamide, polyhexamethylene terephthalamide, andpolyhexamethylene isophthalamide; (flpolycaproamide, polyhexamethyleneterephthalamide, and polyhexamethylene isophthalamide; and (g)polyhexarnethylene adipamide, polycaproamide and polyhexamethyleneterephthalamide. 5. antistatic composition of matter comprising a'polycar'bonamide consisting essentially of a random copolymer ofhexamethylene adipamide and hexamethylene terephthalamide, saidcopolymer containing 6-24 weight percent. aromatic nuclei; and as adistinct phase in the form of small elongated particles from about 1 to15 percent based on the weight of the composition, a high molecularweight poly(alkylene ether) compound formed by the ester interchangereaction of CH3OCCOGH3 8 8 and wherein R is a C -C saturated aliphaticradical, n is an integer, the sum of the ns being 25 to 75, the molratio of (a) to (b) being 1:9 to 1:1. I

6. A fiber shaped from the composition of claim 1. 7. A carpet whosepile is made at least in part of the References Cited UNITED STATESPATENTS Magat 260-857 PG Ohno 260-857 PG Garforth 2'608S7 PG Lofquist260857 PE FOREIGN PATENTS Great Britain 260-857 PG Canada 260857 PGNetherlands 260857 PG Japan 260857 PG Japan 260857 PG Japan 260-857 PGPAUL LIEBERMAN, Primary Examiner fiber of claim 6.

US. Cl. X.R.

1. AN ANTISTATIC COMPOSITION OF MATTER COMPRISING A HIGH MOLECULARWEIGHT FIBER-FORMING POLYCARBONAMIDE WHEREIN THE RECURRING CARBONAMIDELINKAGES ARE AN INTEGRAL PART OF THE POLYMER CHAIN, SAID POLYCARBONAMIDEBEING EITHER A COPOLYMER OF AT LEAST TWO DIFFERENTPOLYCARBONAMIDE-FORMING SUBSTANCES OR A MELT BLEND OF AT LEAST TWODIFFERENT POLYCARBONAMIDE POLYMERS, SAID POLYCARBONAMIDE BEING COMPOSEDOF ABOUT 6-24 WEIGHT PERCENT AROMATIC NUCLEI AND A HIGH MOLECULAR WEIGHTPOLY(ALKYLENE ETHER) AS A DISTINCT PHASE IN THE FORM OF SMAALLELONGGATED PARRTICLES FROM 1 TO 15 PERCENT BASED ON THE WEIGHT OF THECOMPOSITION FORMED BY THE ESTER INTERCHANGE REACTION OF